This invention relates to a display illuminating apparatus for use in a camera, and more particularly to a display illuminating apparatus for illuminating, with electroluminescence, a display device which displays photograph information of a camera.
Liquid crystal display panels, for example, have recently been used in many cases as photograph information display means of cameras. These panels use a light emission diode (LED) or an electroluminescence element (EL) as emission means for rear illumination of the liquid crystal panels.
Japanese Patent Application KOKAI Publication No. 6-67280 discloses a display illuminating apparatus in which a back light consisting of an electroluminescence element is lit using a lighting signal, and extinguished by half pushing its release operation member.
To drive such an EL, it is necessary to use a boosted power voltage. Although a battery such as a lithium ion battery is generally used as the power source of a camera, the EL must be driven by an AC voltage. Moreover, the driving voltage of the EL is higher than the battery voltage. In many cases, the driving voltage is about 100-200V. Thus, to drive the EL, a boosted AC voltage must be used. While boosting a power voltage, however, noise will occur due to changes in power voltage.
Noise that occurs during boosting the power voltage may adversely influence the operations of an auto-focus (AF) system, an auto-exposure (AE) function system, a remote control circuit, etc., which use a fine current.
To avoid such influence, U.S. Pat. No. Re. 30,534, for example, discloses a technique for protecting those systems from the noise. This patent discloses an electronic flash device for a camera, which incorporates a charge control system for inhibiting the charging operation of a flash tube condenser at least during the auto-focusing operation of the camera. This flash device interrupts the charging operation so as to protect, during the auto-focusing operation, the auto-focusing system from the influence of noise generated by the flash unit.
However, U.S. Pat. No. Re. 30,534 does not describe anything about the EL or lighting control for it.
Furthermore, in Japanese Patent Application KOKAI Publication No. 6-67280 first mentioned, all the back light is extinguished where the release operation member is half pushed. Accordingly, the operator of the camera cannot confirm the information on the liquid crystal display panel during the photographing operation.